1. Field of the Invention
The present invention relates to a thermal printer that achieves a reduction in print time.
2. Description of the Related Art
Conventionally, various means have been used in order to reduce the print time in color thermal printers that use thermal recording paper (referred to below as TA (Thermal-Autochrome) paper). One of these involves reducing the fixing time. Namely, in this type of printer, the ink fixing process is performed after the process to heat the thermal recording paper using the thermal head of the printer. This fixing process is carried out by light irradiated from a fluorescent lamp. The energy required to fix the ink is determined using the formula xe2x80x9clight intensityxe2x80x9dxc3x97xe2x80x9cirradiation timexe2x80x9d. Therefore, conventionally, various means have been employed to increase the intensity of the light using reflective plates.
However, conventionally, no means have been employed to strengthen the light emission intensity of the fluorescent lamp.
The present invention was conceived of in view of the above circumstances, and it is an object there of to provide thermal printer in which the light emission intensity of the fluorescent lamp is increased and, as a result, a reduction in the print time is achieved.
The present invention is intended to solve the above problems and the first aspect of the present invention is a thermal printer that performs color printing by carrying out a heating process via a thermal head on thermal recording paper provided with color forming layers for performing color formation in a plurality of different colors and by fixing the thermal recording paper that has undergone heating process using a light fixing device, wherein the light fixing device comprises: a hot cathode fluorescent lamp formed from: a fluorescent tube that has a fluorescent coating applied to an inside surface of the glass tube and inside which are sealed mercury and noble gases, filament electrodes provided at both ends of the fluorescent tube, and lead wires that supply power to the filament electrodes; and a magnetic circuit that is provided on a side surface of the fluorescent tube and that generates a magnetic field that acts on current that flows through the fluorescent tube when power is fed to the filament electrodes.
According to the present invention, in a thermal printer that performs color printing by carrying out a heating process on thermal recording paper using a thermal head and then fixing the thermal recording paper that has undergone the heat processing using light fixing device, because the light fixing device is formed from a hot cathode fluorescent lamp and a magnetic circuit that is provided on a side surface of the fluorescent tube and that generates a magnetic field that acts on the current flowing through the fluorescent tube when electricity is fed to the filament electrode, it is possible to increase the light emission intensity of the fluorescent lamp without shortening the life of the hot cathode fluorescent lamp. Moreover, the effective length of the fluorescent tube is improved by flattening the illumination intensity distribution by the illumination intensity in the vicinity of the filament electrodes being increased due to the magnetic circuit. As a result, the excellent effects are obtained that the print time is shortened, and uniform fixing can be made possible with unfixed areas or over fixed areas being done away with. Furthermore, because it is possible to maintain the maximum illumination intensity for a long period of time by providing a cooling fan for cooling the fluorescent tube, the excellent effect is obtained that the operating efficiency is vastly improved when the hot cathode fluorescent lamp is used for hardening resins that are hardened by ultraviolet light or for sterilization.
The second aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises a frame formed with a U shaped cross section from a ferromagnetic material, and a pair of magnets positioned such that different polarities face each end of the frame, and wherein the magnetic circuit is mounted on a side surface of the fluorescent tube so as to surround a lower half of the fluorescent tube.
The third aspect of the present invention is the thermal printer according to the second aspect, wherein a reflective plate is disposed between an end portion of the magnets and the fluorescent tube.
The fourth aspect of the present invention is the thermal printer according to the second aspect, wherein a surface of the magnets that faces the fluorescent tube is curved in a shape that substantially corresponds to a surface of the fluorescent tube, and that curved surface forms the reflective plate.
The fifth aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises a frame formed with a U shaped cross section from a ferromagnetic material, and a pair of magnets provided at both ends of the frame, and wherein a plurality of magnets are mounted in a row on a side surface of the fluorescent tube so as to surround a lower half of the fluorescent tube and so that polarities of adjacent magnets are different to each other.
The sixth aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises four magnets positioned at equal intervals along a peripheral surface of the fluorescent tube so that polarities of adjacent magnets are different to each other.
The seventh aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises a magnet shaped as a semicylinder, and more than half of an outer peripheral surface of the fluorescent tube is surrounded by a concave portion of the magnet.
The eighth aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises: a frame formed with a U shaped cross section from a ferromagnetic material and mounted so as to surround half a side surface of the hot cathode fluorescent lamp; and a pair of magnets positioned such that different polarities face each end of the frame and so as to sandwich one filament electrode of the hot cathode fluorescent lamp and a portion of the fluorescent tube.
The ninth aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises: a frame formed with a U shaped cross section from a ferromagnetic material and mounted so as to surround half a side surface of the hot cathode fluorescent lamp; and two pairs of magnets positioned such that different polarities face each end of the frame and so as to sandwich the filament electrodes at both ends of the hot cathode fluorescent lamp and a portion of the fluorescent tube.
The tenth aspect of the present invention is the thermal printer according to the eighth and ninth aspects, wherein a magnet used in the magnetic circuit is in a rectangular shape, a rectangular shape having one curved side, or a rectangular shape whose central portion has a different thickness to both end portions.
The eleventh aspect of the present invention is the thermal printer according to the first aspect, wherein the magnetic circuit comprises: a frame formed with a U shaped cross section from a ferromagnetic material and mounted so as to surround half a side surface of the hot cathode fluorescent lamp; and a pair of magnets mounted at both ends of the frame so as to sandwich the fluorescent tube; and two pairs of magnets positioned at both ends of the frame so as to sandwich the filament electrodes at both ends of the hot cathode fluorescent lamp and a portion of the fluorescent tube.
The twelfth aspect of the present invention is the thermal printer according to the eleventh aspect, wherein a magnet used in the magnetic circuit is in a rectangular shape, a rectangular shape having one side formed in a wave shape, or a rectangular shape whose thickness is formed in a wave shape.
The thirteenth aspect of the present invention is the thermal printer according to any one of the first to twelfth aspects, wherein a magnet used in the magnetic circuit is a ferrite magnet or a rare earth permanent magnet such as a samarium cobalt magnet.
The fourteenth aspect of the present invention is the thermal printer according to any of the first to twelfth aspects, wherein a magnet used in the magnetic circuit is an electromagnet formed from a soft porcelain material and a coil wound around the soft porcelain material.
The fifteenth aspect of the present invention is the thermal printer according to any of the first to fourteenth aspects, wherein the hot cathode fluorescent lamp is provided with a cooling fan at each end of the fluorescent tube for cooling the fluorescent tube.
The sixteenth aspect of the present invention is the thermal printer according to the fifteenth aspect, wherein the number of rotations of the cooling fan is controlled based on a surface temperature and illumination intensity of the fluorescent tube such that the illumination intensity is at maximum.
The seventeenth aspect of the present invention is a thermal printer comprising: moving device which moves thermal recording paper that is provided with color forming layers for performing color formation in a plurality of different colors in a first direction and in a second direction that is opposite to the first direction while the thermal recording paper is in a state of contact with a thermal head; first light fixing device provided at one side of the thermal head for fixing a first color; and second light fixing device provided at another side of the thermal head for fixing a second color, wherein the first and second fixing device comprise: a hot cathode fluorescent lamp formed from: a fluorescent tube that has a fluorescent coating applied to an inside surface of a glass tube and inside which are sealed mercury and noble gases, filament electrodes provided at both ends of the fluorescent tube, and lead wires that supply power to the filament electrodes; and a magnetic circuit that is provided on a side surface of the fluorescent tube and that generates a magnetic field that acts on current that flows through the fluorescent tube when power is fed to the filament electrodes.
According to the seventeenth aspect of the present invention, because there is no need to perform an operation to return the photosensitive material each time the printing of one color is completed, the effect is obtained that the time required to perform the printing operation can be shortened. In addition, according to the nineteenth aspect of the present invention, the effect is obtained that it is possible for the color formation of each color to be carried out at a predetermined position without there being any misalignment in the printing position.
The eighteenth aspect of the present invention is the thermal printer according to the seventeenth aspect, wherein the moving device is formed from a first pinch roller and a first feed roller provided at one adjacent side portion of the thermal head, a second pinch roller and a second feed roller provided at another adjacent side portion of the thermal head, and a pulse motor for driving the first and second feed rollers.
The nineteenth aspect of the present invention is the thermal printer according to the eighteenth aspect, the thermal printer further comprising: a first sensor provided in the vicinity of the first pinch roller and first feed roller for detecting a leading edge of the thermal recording paper; a second sensor provided in the vicinity of the second pinch roller and second feed roller for detecting a leading edge of the thermal recording paper; and printing start position determining device which supplies the pulse motor with a pulse number that is in accordance with a distance that a printing start position of the thermal recording paper is to be moved in order to be directly below the thermal head, based on results of detections by the first sensor and second sensor.
The twentieth aspect of the present invention is the thermal printer according to the thirteenth or nineteenth aspects, wherein there is provided a shutter for shutting off light from the first light fixing device at a point when fixing of the first color is completed.
The twenty first aspect of the present invention is a method of designing a hot cathode fluorescent tube that has a magnet and is structured such that a magnetic filed generated by the magnet acts on an electron flow so as to increase an illumination intensity, the method comprising: (a) a first step in which an empirical formula for representing a relationship between illumination intensity and magnetic energy density is derived from measurement values of illumination intensity and magnetic flux density inside the hot cathode fluorescent tube; (b) a second step in which initial values for a shape of the magnet are set; (c) a third step in which a model of the hot cathode fluorescent tube is created to be used for applying a finite element method; (d) a fourth step in which an evaluation coefficient that serves as an index for evaluating the shape of the magnet is derived using the empirical formula; and (e) a fifth step in which the finite element method is applied to the hot cathode fluorescent tube model and the shape of the magnet that was set to the initial values is optimized using the evaluation coefficient.
According to the twenty first aspect of the present invention, because the shape of the magnets is decided by numerical analysis, it is possible to optimize the magnet shape without having to rely on experience or intuition and the make the illumination intensity uniform over the entire effective length of the fluorescent tube.
The twenty second aspect of the present invention is the method of designing a hot cathode fluorescent tube according to the twenty first aspect, wherein, in the first step the magnetic flux density inside the hot cathode fluorescent tube and the illumination intensity when the magnet is mounted inside the hot cathode fluorescent tube are measured and the empirical formula is determined from the relationship between the illumination intensity and the magnetic flux density.
The twenty third aspect of the present invention is the method of designing a hot cathode fluorescent tube according to the twenty first or twenty second aspects, wherein, in the fourth step "khgr"=(Eobj/Eavxe2x88x921)2 is used as the evaluation coefficient when Eobj is taken as the illumination intensity when the magnet is not mounted and Eav is taken as the average illumination intensity when the magnet is mounted.